1. Field of the Invention
The present invention relates to an acoustic apparatus which can supply a specific frequency band component signal of a driving signal to a loudspeaker unit and, more particularly, to an acoustic apparatus which is arranged without using a passive dividing network, and is driven by a conventional external power amplifier unit like in a conventional apparatus using the passive dividing network.
2. Description of the Prior Art
As a conventional system for driving a multi-way loudspeaker system, e.g., the system having a woofer, squaker, tweeter, or the like, a dividing network system and a multi-amplifier system are known.
However, the dividing network system requires large-capacity LC real elements. For this reason, this network system poses the following problems:
(1) A reproduced sound is distorted by a magnetic distortion of an inductance element (in particular, the distortion is conspicuous when a cutoff frequency f.sub.c of a filter constituting a network is decreased).
(2) An element inevitably becomes large in size since a core of an inductance element must be increased in size to reduce the magnetic distortion.
(3) Serial resistances of a loudspeaker unit and a driving system are increased due to a resistance of a coil of an inductance element, and Q of the loudspeaker unit is increased and cannot be damped.
(4) In addition, an AC nonpolarized (bipolar) capacitor having a large capacitance is required. In general, tan .delta. is small, and precision of a capacitance (i.e., dividing precision) is also low.
(5) Since a load is not a pure resistance but a impedance of a loudspeaker is changed depending on a frequency, it is difficult to design network characteristics.
(6) When an attenuator or the like is arranged to adjust, e.g., frequency characteristics of an output sound pressure, damping characteristics or the like are further adversely influenced.
On the other hand, the multi-amplifier system can solve the problems in the dividing network system. However, the multi-amplifier system must systematically deal with the entire system including a channel divider, power amplifiers in units of frequency bands, and the like, and can never be a loudspeaker system in which a loudspeaker system and an amplifier can be arbitrarily selected, i.e., which can be driven by an amplifier selected by a user.